90% of the time the diagnostic tool sees the snippet; we've had a handful of occasions where it doesn't and it's more the lack of consistency that makes me dubious about setting the test live. Be interested to see what they say.

Don't take the Diagnostic Report's word as the law. I'd advise you to consider it as a helpful nudge that reminds you to double-check the snippet is on the page, but so long as you can confirm that is the case, ignore any further error messages it shows.

Here are a few reasons why you might get an error message in the Diagnostic Report although the snippet is on the page:

1) The snippet has been modified and the Diagnostic Report can no longer recognise it in its new form. This looks like it might be the case for you.

2) The snippet is not defined natively on the page, but is instead installed via an external script or tag manager. If the snippet is not defined natively, the Diagnostic Report cannot find it.

3) Your page is being loaded via proxy. You can check this by opening up the browser console once the experiment has loaded in the editor and searching for an object called "loader". If you expand the object, you'll be able to see whether the page has loaded via HTTPS, HTTP or proxy. If the page is loaded over proxy, the editor inserts a temporary snippet and the Diagnostic Report returns an error.

In all three cases, you can safely ignore the error message since you already know the snippet is on the page.

In any case, I hope this sheds some light on how the Diagnostic Report works.